A comprehensive approach to DOA estimation using higher-order statistics

The algorithms developed in this paper rely on cumulants, or higher-order statistics, to eliminate Gaussian noise. A simple relation between the signal model parameters and the cumulant matrices computed from the received signals forms the basis for the development of these algorithms. The block Hankel structure of matrices formed from the cumulant matrices enables the directions of arrival (DOAs) to be estimated using the well-known MUSIC and ESPRIT approaches to DOA estimation. The effectiveness of the methods proposed here is demonstrated by the results of extensive computer simulation studies.This work was supported by the National Sciences and Engineering Research Council of Canada.     

A comprehensive CAD approach to the design of MMICs up to mm-wavefrequencies

A comprehensive computer-aided design (CAD) approach has been developed that forms the core of a layout-oriented, process-independent simulator for an MMIC (monolithic microwave integrated circuit) design engineering workstation (EWS). The CAD solutions developed and in progress for EWS are described. The solutions include a field-theory-based, high-resolution generator which produces the modal characteristics of complex MMIC microstrip structures. Another portion used as a support tool is a three-dimensional, hybrid-mode-based analysis package for discontinuities, nonelementary rectangular conductor patterns, and the analysis of coupling problems. Thus, the layout-oriented analysis and optimization scheme developed can handle interdigitated and spiral components as well as complex coding situations     

A hierarchical approach to large circuit symbolic simulation

This paper presents a new approach to symbolic analysis of large circuits. The proposed procedure is grounded on circuit decomposition by node tearing, symbolic analysis at subcircuit level and circuit function generation. Symbolic analysis is based on matrix-determinant method implemented within our original symbolic simulator. The crucial part of this procedure is circuit function generation. Opposed to classic symbolic simulation that gives final result in canonical sum-of-product form, hierarchical approach results in compact nested form. Proposed method is described in details using a simple example. The comparison with two other similar techniques is given using a benchmark example. The overall time reduction in comparison with the circuit function extraction in fully expanded form is 30 times.     

A frequency-domain approach to interconnect crosstalk simulation and minimization

A frequency-domain approach to efficiently simulate and minimize the crosstalk between high speed interconnects is proposed in this paper. Several methods for modeling coupled microstrip transmission lines are discussed. Several possible simulation strategies are also considered. A straightforward yet rigorous frequency-domain approach is followed. This approach can be used for linearly and non-linearly terminated microstrip coupled lines, since it exploits the harmonic balance technique. A typical example of microstrip interconnects is simulated and the results are compared with those obtained in previous work by other authors using time-domain methods. The simulation method proposed in this work yields good accuracy. A crosstalk minimization problem is formulated and solved following the method proposed.     

A distributed fixed-step power control algorithm with quantizationand active link quality protection

A distributed fixed-step power control algorithm is presented. It is a simple feedback adjustment algorithm using only local information. In the ideal case where there is no power constraint, it is guaranteed that existing users will not be dropped due to admission of new users. If it is infeasible to accommodate all of them, the new user will be blocked. When the constraint on the maximum power is imposed, it is shown by simulation that blocking a new call is more probable than dropping any existing calls, if the capacity is exceeded. Besides, its convergence property is demonstrated. The convergence rate, which depends on the step size, is studied through simulation. In addition, the issue of power quantization is addressed     

A comprehensive approach to the analysis of contrast enhanced cardiac MR images

Current magnetic resonance imaging (MRI) technology allows the determination of patient-individual coronary tree structure, detection of infarctions, and assessment of myocardial perfusion. Joint inspection of these three aspects yields valuable information for therapy planning, e.g., through classification of myocardium into healthy tissue, regions showing a reversible hypoperfusion, and infarction with additional information on the corresponding supplying artery. Standard imaging protocols normally provide image data with different orientations, resolutions and coverages for each of the three aspects, which makes a direct comparison of analysis results difficult. The purpose of this work is to develop methods for the alignment and combined analysis of these images. The proposed approach is applied to 21 datasets of healthy and diseased patients from the clinical routine. The evaluation shows that, despite limitations due to typical MRI artifacts, combined inspection is feasible and can yield clinically useful information.     

A comprehensive, automated approach to determining sea icethickness from SAR data

Documents an approach to sea ice classification through a combination of methods, both algorithmic and heuristic. The resulting system is a comprehensive technique, which uses dynamic local thresholding as a classification basis and then supplements that initial classification using heuristic geophysical knowledge organized in expert systems. The dynamic local thresholding method allows separation of the ice into thickness classes based on local intensity distributions. Because it utilizes the data within each image, it can adapt to varying ice thickness intensities to regional and seasonal changes and is not subject to limitations caused by using predefined parameters     

A holistic concurrent design approach to robotics using hardware-in-the-loop simulation

This paper discusses a practical approach to the concurrent design of robot manipulators, which is based on an alternative design methodology, namely Holistic Concurrent Design (HCD), as well as the utilization of a modular hardware-in-the-loop simulation. Holistic concurrent design is a systematic design methodology for mechatronic systems that formalizes subjective notions of design, resulting in the simplification of the multi-objective constrained optimization process. Its premise is to enhance the communication between designers with various backgrounds and customers, and to consider numerous design variables with different natures concurrently. The methodology redefines the ultimate goal of design based on the qualitative notion of satisfaction, and formalizes the effect of designer’s subjective attitude in the process. The hardware-in-the-loop platform involves physical joint modules and the control unit of a manipulator in addition to the software simulation to reduce modeling complexities and to take into account physical phenomena that are hard to be captured mathematically. This platform is implemented in the HCD design architecture to reliably evaluate the design attributes and performance supercriterion during the design process. The resulting architecture is applied to redesigning kinematic, dynamic and control parameters of an industrial manipulator.     

A recursive free-body approach to computer simulation of human postural dynamics

A recursive, free-body approach to the estimation of joint torques associated with observed motion in linkage mechanisms has recently been shown to be computationally more efficient than any other known approach to this problem. This paper applies this method to the analysis of human postural dynamics and shows how it can also be used to compute accelerations for specified joint torques. The latter calculation, referred to here as the direct dynamics problem, has until now involved symbolic complexity to such an extent as to generally limit computer simulation studies of postural control to very simple models. The model presented in this paper is both straightforward and general, and removes this obstacle to the investigation of possible neural control mechanisms by means of computer simulation. A computationally oriented linearization procedure for the direct dynamics problem is also included in the paper. Finally, example simulation results and corresponding measured body motions for human subjects are presented to validate the method.     

A new approach to the modeling of converters for SPICE simulation

An approach to the modeling of DC-DC converters for SPICE simulation is developed in which the average current in the energy-storage inductor is first simulated in a SPICE subcircuit for both the continuous and discontinuous modes of operation. The inductor current is then weighted and redistributed to related branches of the circuit to simulate the average input and output currents of the converter. Based on this technique, various converter models, including that of the Cuk converter with coupled inductors, which are valid for both continuous and discontinuous modes of operation, are developed     

A comprehensive two-dimensional VLSI process simulation program, BICEPS

Bell Integrated Circuit Engineering Process Simulator (BICEPS) is a comprehensive VLSI process-simulation program developed at Bell Laboratories. BICEPS incorporates the most up-to-date physical models and efficient numerical algorithms to make it a highly robust and general-purpose program. BICEPS can calculate doping profiles resulting from ion implantation, predeposition, oxidation, and epitaxy in one or two spatial dimensions as well as etching and deposition of oxide, nitride, and photoresist. In this paper, the physics of IC process simulation will be reviewed with an emphasis on the various physical models implemented in BICEPS. Calculation of the impurity profiles in VLSI devices involves the solution of a coupled set of nonlinear time-dependent partial differential equations, with moving boundaries and in more than one spatial dimension. The numerical techniques in obtaining a solution to this problem, namely, spatial discretization, time discretization, and the treatment of moving boundaries are also described in this paper. The capabilities of BICEPS are illustrated by the results of simulation of the fabrication of a typical NMOS transistor.     

Lattice-gas approach to semiconductor device simulation

A new approach to semiconductor device simulation is presented which is based on a lattice-gas or cellular-automata model and is quite similar to methods recently explored in fluid dynamics. The approach obtains a stochastic solution to the diffusion-drift partial differential equations describing electron transport in semiconductors. The lattice-gas method appears to be fairly well-suited to electron transport simulation with its ability to handle complex geometry, its ease of programming and its stability being some key advantages. In addition, we show that the structure of the model itself—its Boolean character—leads to a partial inclusion of electron degeneracy effects. Finally, we make a preliminary assessment of the performance of the diffusion-drift lattice-gas model, finding it to be competitive with conventional approaches when its inherent parallelism is fully exploited.     

A qualitative approach to cell growth modeling and simulation forcancer chemotherapy

A qualitative model of cell growth that is based on qualitative process theory is presented. The model can be used to analyze the effects of the interaction of antiproliferative drugs on cells when the effects of each specific drug are known, which is useful when designing multidrug protocols for optimal cancer treatment. This model encompasses both structural and behavioral aspects. This makes it suitable for drawing conclusions about differences among different types of cell growth and about system behavior under different situations. adding some significant options with respect to closed-form cell cycle models. Moreover, qualitative modeling, unlike closed-form modeling, allows causal explanations of events: in this respect, the qualitative simulation presented-based on reasoning in terms of processes, individual views. and history limits-makes causes of specific behaviors even clearer than qualitative simulation based on constraints. This model is able to adapt to the amount of information supplied by the user: if this is scarce (only relating to the cell cycle phase on which each drug acts), the model will produce a simulation in which only cell cycle phase information for the combination is present; if the information supplied is more detailed, the simulation output will be more detailed as well     

A new approach to the simulation of small-signal current gains ofpnpn structures

An approach to the mathematical simulation of small-signal current gains (alphas) versus frequency that respects Fulop's measuring procedure is proposed, using an arrangement close to the real measuring circuit. For this purpose, an exact 1-D mathematical model is used. The dependence of small-signal alphas on the anode current of a high power thyristor (GTO) was found to be in agreement with measurements for low anode-to-cathode voltage     

A simulation approach for computing systems reliability

The basis of the concept of reliability is that a given component has a certain stress-resisting capacity; if the stress induced by the operating conditions exceeds this capacity, failure results. Most of the published results in this area are based upon analytical modelling of stress and strength, using various probability distributions, and then trying to find an exact expression for system reliability, which can be very difficult to obtain sometimes. The approach used in this paper is very simple and uses simulation techniques to repeatedly generate stress and strength of a system by the computer, using a random number generator and methods such as the inverse transformation technique. The advantage of this approach is that it can be used for any stress-strength distribution functions. Finally, numerical results obtained from using this approach are compared with results obtained using the analytical methods for various strength-stress distribution functions, such as exponential, normal, log normal, gamma and Weibull. Results show the viability of the simulation approach.     

A comprehensive simulation model for immunity prediction in integrated circuits with respect to substrate injection

This paper presents a comprehensive modelling methodology for the electromagnetic immunity of integrated circuits (ICs) to direct power injection (DPI). The aim of this study is to predict the susceptibility of ICs by the means of simulations performed on an appropriate electrical model of different integrated logic cores located in the same die. These cores are identical from a functional point of view, but differ by their design strategies. The simulation model includes the whole measurement setup as well as the integrated circuit under test, its environment (PCB, power supply) and the substrate model of each logic core. Simulation results and comparisons with measurement results demonstrate the validity of the suggested model. Moreover, they highlight the interest of the aforementioned protection strategies against electromagnetic disturbances.     

A novel approach to modeling and efficient simulation offrequency-selective fading radio channels

A multipath radio channel concept based on channel orthogonalization techniques in two inner product spaces is presented and compared to the conventional approach of modeling each individual Rayleigh or Rice fading multipath ray individually. The proposed simulator can be applied to linear amplitude/phase modulation and linear fading channels including Nyquist filtering. It is shown to be a good approximation to the conventional model in the case of tight rolloff factors. Channels having quasi-or truly continuous delay profiles can now be properly represented at significantly reduced computational complexity. The proposed simulation concept leads to the lowest level of complexity being achieved for the prevailing channel and noise conditions on a particular channel     

Mean acquisition time analysis of fixed-step serial search algorithms

In this paper, mean acquisition time (MAT) analysis of fixed-step serial search (FSSS) algorithms is presented. First, it is shown that the MAT of an FSSS algorithm can be obtained from that of a conventional serial search (CSS) algorithm after a certain mapping of the uncertainty region. Then, a generic formula for the MAT of FSSS algorithms is derived, which is valid for both dense and sparse channel environments. In addition, MAT formulas for high signal-to-noise ratio scenarios, for large uncertainty regions, and for dense channels are obtained as special cases of the generic solution. Finally, simulation results are presented to verify the analysis and to investigate the factors that affect the optimal step size for FSSS algorithms.     

A building block approach to the design and simulation of complex current-memory circuits

A building block approach to the design and simulation of complex current-memory circuits is described. Sampled-data techniques are used to simulate the operation of networks containing a great number of cells. The main building block is the current-memory cell itself, which has been carefully modeled including charge injection and noise. The proposed model has been compared to SPICE simulations on several small examples, and excellent agreement is obtained. Simulation of complex circuits is orders of magnitude faster than a full time-domain simulation with SPICE. The usefulness of the approach is demonstrated through the design and simulation of a current-memory based second order — modulator. The complete characterization of the signal-to-noise and distortion ratio can be achieved in about 4 hours of CPU time on an advanced workstation.This work was partly supported by THOMSON-SINTRA ASM under grant 91.C42.284.     

A three-scale approach to the numerical simulation of metallic bonding for MEMS packaging

In this work we present a numerical, multi-scale approach to estimate the strength of a wafer-to-wafer metallic thermo-compression bonding. Following a top-down approach, the mechanical problem is handled at three different length scales. Taking into account control variables such as temperature, overall applied force over the wafer and contact surface roughness, it is shown that the proposed approach is able to provide an estimate of the sealing properties, especially in terms of bonding strength.